Stage 2 load shedding will be implemented from 12:00 on Friday due to an increase in generation unit breakdowns that led to a loss of capacity exceeding 3 000 MW, Eskom said in a statement.
This will continue until 22:00, with pressure on the grid expected to last over the weekend.
"While five generation units were taken off the grid last night and this morning, a breakdown at the Matimba power station has today resulted in the need for load shedding," Eskom said.
Two units at Arnot, as well as a unit each at Kendal, Tutuka and Majuba were taken off the grid last night and this morning, adding up to the loss of 3 000 MW.
There was also a delay in the return to service of a unit at Duvha.
Eskom has managed to avoid load shedding thus far during the lockdown, although Gauteng has faced bouts of localised rolling blackouts known as "load rotation", which Eskom has attributed to a prevalence of vandalism and illegal connections.
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